What is glucose
Glucose is a simple sugar (monosaccharide) and the primary source of energy for cells in the body. It has the chemical formula C₆H₁₂O₆ and is the most important carbohydrate in biology.
Key facts:
- Structure: A 6-carbon aldose sugar, existing mainly in a ring form (pyranose) in solution
- Energy currency: Cells break it down via glycolysis, the citric acid cycle, and oxidative phosphorylation to produce ATP
- Sources: Comes from dietary carbohydrates (starch, sucrose, lactose), and can be made internally via gluconeogenesis in the liver
- Blood glucose: Normally maintained at 70-100 mg/dL (fasting) by insulin (lowers it) and glucagon (raises it)
- Storage: Stored as glycogen in the liver and muscles; excess is converted to fat
- Medical relevance: Central to diabetes mellitus - Type 1 (no insulin production) and Type 2 (insulin resistance) both cause chronically elevated blood glucose (hyperglycemia)
Metabolism overview:
- Glycolysis - glucose → pyruvate (in cytoplasm, yields 2 ATP net)
- Pyruvate → acetyl-CoA → enters citric acid cycle
- Oxidative phosphorylation yields ~30-32 ATP total per glucose molecule
Clinical uses: IV dextrose (D5W, D50W) for hypoglycemia, glucose tolerance tests for diagnosing diabetes, and glucose monitoring is a cornerstone of diabetes management.
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